On outdoor stairs, in industrial plant and anywhere that gets washed down, aluminium nosings have a limited life. Salt corrodes them, chemicals pit them, and smooth metal loses grip the moment it gets wet. GRP — glass reinforced plastic — is the specification that replaces them, and it is the only common nosing material that carries its slip resistance all the way through the product rather than on the surface.
This guide covers what GRP is, how slip resistance is actually measured in the UK, which profile and grit to specify, and how to fit it so it lasts.
What GRP is
GRP, also sold as fibreglass or FRP, is a composite of four parts:
- Resin matrix — polyester or epoxy, roughly 30–40% by weight. Provides chemical resistance and binds the structure.
- Glass fibre reinforcement — roughly 60–70% by weight. Delivers strength and rigidity.
- Anti-slip aggregate — silicon carbide or aluminium oxide, bonded into the surface layer rather than sprinkled on top.
- UV stabilisers and pigment — prevent chalking and fade. The colour runs through the material.
That last pair is the practical difference from a painted or coated nosing. There is no surface film to wear through, so grip and colour degrade together with the material rather than peeling off it.
How slip resistance is actually measured
This is where most stair nosing specifications go wrong, so it is worth getting straight before you compare products.
You will see two numbers quoted. They measure different things and they cannot be converted into one another.
| Pendulum Test Value (PTV) | R rating | |
|---|---|---|
| Standard | BS 7976, now BS EN 16165 | DIN 51130 |
| Method | Swinging rubber slider | Person walks a tilting ramp |
| Contaminant | Water | Motor oil |
| Footwear | Standard rubber slider | Safety boots |
| Can test in situ? | Yes | No, laboratory only |
| Recognised by HSE | Yes — the preferred method | No |
Why this matters commercially: a single R10 rating covers pendulum results anywhere from 20 to 60 PTV — the full span from high slip potential to low. Specifying by R rating alone tells you remarkably little about how a surface behaves in the rain, and PTV is the figure that carries weight with the HSE and in court.
The HSE and the UK Slip Resistance Group classify wet pendulum results on a simple scale: 0–24 is high slip potential, 25–35 is moderate, and 36 or above is low. PTV 36 wet is the benchmark to specify against.
Quality GRP clears it comfortably. Published UK supplier data puts GRP nosings around 65–69 PTV wet, with some silicon-carbide products exceeding 80 PTV wet — roughly double the threshold. That headroom is the whole argument for GRP on an external or wash-down stair, and it is why the material dominates in marine and food-production settings where a wet floor is the normal condition rather than the exception.
R ratings still have their place: R11 and above is the usual shorthand for industrial specification, and it is genuinely informative where oil rather than water is the contaminant. Ask for both figures, and treat any supplier who can only give you one as an incomplete answer.
GRP against the alternatives
| Factor | GRP | Aluminium | Rubber | Concrete |
|---|---|---|---|---|
| Wet slip resistance | Excellent (65–80+ PTV) | Depends on insert | Good, falls with wear | Moderate |
| Weather resistance | Excellent | Good, can corrode | Poor, UV degrades | Excellent |
| Chemical resistance | Excellent | Poor | Moderate | Moderate |
| Salt and coastal | Unaffected | Corrodes | Degrades | Good |
| Conductivity | Non-conductive | Conductive | Non-conductive | Non-conductive |
| Grip when worn | Holds — aggregate runs through | Insert replaceable | Falls away | Polishes smooth |
| Appearance options | Limited, functional | Wide, anodised or coated | Limited | None |
| Fire | Class 1/2 grades available (BS 476 Pt 7) | Non-combustible (A1) | Combustible | Non-combustible |
When GRP is the right call
- Outdoor exposure — rain, ice, UV and temperature swings
- Coastal and marine — salt spray attacks aluminium quickly; GRP is unaffected
- Chemical exposure — industrial sites, laboratories, agricultural buildings
- Wash-down regimes — food production, commercial kitchens, car washes
- Electrical safety — GRP is non-conductive, which matters near live plant
Where none of those apply — a dry internal office stair — aluminium is usually the better-looking and cheaper answer. GRP is a performance material, not a default.
Which GRP product you actually need
"GRP nosing" covers four distinct products, and picking the wrong one is the most common specification error:
- Nosing covers protect the step edge only. The default retrofit and the cheapest way to make an existing stair safe. See the 70mm × 30mm GRP nosing cover.
- Tread covers sheet the whole tread, not just the edge. Specify where the tread surface itself is worn or slippery, as with the 4mm hazard-marked tread covers.
- Replacement treads rebuild the step entirely, for stairs with structural damage or poor original construction.
- Landing covers and strips continue the same surface across landings and walkways, so grip does not change underfoot at the top of a flight — a common and overlooked failure point.
The full GRP stair nosing and tread range covers all four.
Profiles and sizing
GRP nosings run from about 25mm to 100mm of tread coverage. Two profiles do most of the work, and both are industry standard across UK suppliers:
- 55mm × 55mm — equal coverage on tread and riser. This matches the contrasting band described in Approved Document M, which makes it the usual choice for public and non-domestic buildings. Available in black and high-visibility yellow.
- 70mm × 30mm — more tread, less riser. The wider tread covers the zone where foot traffic concentrates, and the shallower riser face accommodates existing edge damage without substrate levelling. The retrofit workhorse.
Typical thickness is 3–6mm, enough for rigidity without creating a trip lip. Look for a chamfered leading edge, which resists chipping, and factory pre-drilled countersunk holes at around 150mm centres. Stock lengths generally run from 400mm to 3m, with bespoke lengths available on project quantities.
Grit grade
- Fine — around 0.5mm aggregate. Barefoot areas: pools, changing rooms, spa
- Medium — around 1mm. General purpose, and the right default for most stairs
- Coarse — heavy industrial and oil-contaminated steps. Maximum grip, rough underfoot, and unsuitable anywhere people may fall onto it
Colour
Black, yellow, white, grey, green and red are all standard, with RAL matching on volume orders. Yellow is the usual specification for hazard areas and loading bays; black hides dirt and contrasts well against pale concrete; white suits healthcare and food production. Colour is not only cosmetic here — see the contrast requirement below.
Where GRP gets specified
Outdoor stairs
Schools, libraries, council offices and community centres combine weather exposure with heavy footfall. GRP removes the repaint-or-replace cycle that rubber and painted finishes need. External fire escapes, garden steps and patio access get the same benefit.
Industrial
Warehouses and distribution centres put forklift and pallet-truck loads through step edges. Manufacturing plant adds chemical spills and aggressive cleaning regimes that destroy aluminium and rubber. Food processing adds high-pressure washing with sanitisers, which GRP tolerates without losing grip.
Marine and coastal
Salt spray is the fastest route to aluminium failure. Marinas, boatyards, seafront buildings, beach access steps and promenades are where the difference in service life is starkest.
Wet areas
Pools and leisure centres combine constant water with chlorine or bromine. Shower and changing facilities need grip that does not depend on a coating staying intact — and in barefoot areas, fine grit rather than medium. GRP strips extend the same surface onto decking, ramps and walkways nearby.
Installation
Before you start
GRP tolerates an uneven substrate better than aluminium, but severe damage still needs repairing. Fill major cracks and spalls with epoxy repair mortar and let it cure fully. Clean the step edge back to sound material — dirt, oil, loose fragments and old adhesive all have to go. Concrete and masonry must be dry before any adhesive is used; damp substrate is the usual cause of bond failure.
One difference from aluminium worth knowing before you order: GRP is rigid and cannot be bent or eased to fit on site. Measure each step properly, because there is no adjusting it afterwards.
Mechanical fixing — the default
- Measure and cut. Angle grinder with a cutting disc, fine-tooth saw or hacksaw. GRP cuts cleanly but throws glass fibre dust, so wear a mask and eye protection and work in ventilated space. File the cut edge to remove splinters.
- Position. Leave 2–3mm clearance at each end so thermal movement does not bind and crack the nosing.
- Mark through the pre-drilled holes. Every hole on concrete; every second hole is usually enough on steel.
- Drill. 6mm masonry bit and nylon plugs for concrete, 4mm for steel. Drill about 5mm deeper than the screw.
- Fix. Stainless steel countersunk screws — A4 grade in coastal and marine work, where A2 will still pit. Start at the centre and work outwards. Tighten until flush, then roughly a quarter turn more; over-torquing cracks GRP around the hole.
- Check. Sight along the run with a straight edge. A crooked nosing is a trip hazard as well as an eyesore.
Adhesive fixing
For smooth concrete, tiled steps, or anywhere drilling is prohibited — listed buildings and some tenancies. Not suitable for rough or porous substrates. Use a two-part epoxy or polyurethane construction adhesive; ordinary contact adhesives do not develop enough bond strength.
Degrease the substrate with acetone or isopropanol, abrade the underside of the nosing with 60-grit paper, apply adhesive in continuous beads along the length, press down across the full surface, then weight or clamp until cured — typically 24 hours at 20°C. Substrate temperature needs to be above 5°C for a reliable cure, so mechanical fixing is the winter option.
Hybrid
For hospitals, care homes and public buildings, adhesive for continuous support plus mechanical fixings for redundancy.
Mistakes that cause callbacks
- Skipping fixings to save time, which creates flex points between screws
- Zinc-plated screws outdoors — they corrode and stain. Stainless only
- Over-tightening, which cracks the material around the countersink
- Fixing to damp substrate, which fails the adhesive and traps water
- Cutting to the exact step width, leaving no expansion clearance
- Coarse grit in a barefoot area, which is a laceration risk rather than a safety measure
Full detail is in our step-by-step installation guide.
Service life and maintenance
GRP needs no painting, sealing or protective treatment. Because the aggregate is bonded through the surface layer rather than applied to it, slip resistance holds up as the surface wears — which is the single biggest practical advantage over any coated or painted alternative.
Guaranteed life is ten years across our GRP nosings and tread covers, and in practice installations routinely run well beyond that in sheltered and internal locations. Coastal, chemical and heavy industrial settings sit at the shorter end. Anyone quoting a single number for every environment is guessing.
- Weekly — sweep or vacuum to stop organic staining building up
- Monthly — pressure wash or scrub with detergent. Any normal cleaner is fine
- Quarterly — check fixings and retighten anything that has worked loose
On a stair where slip risk has been formally assessed, the sensible addition is a periodic pendulum test in situ. Because PTV can be measured on the installed surface, you can evidence that a stair still performs rather than assuming it does.
What the UK rules actually require
These get quoted loosely, and the difference between a legal requirement and a recommendation matters when you are specifying:
- The Workplace (Health, Safety and Welfare) Regulations 1992, regulation 12 — this one is law. Floors and traffic routes must be of suitable construction and must not be slippery so as to expose anyone to a risk to their health or safety. This is the duty that actually bites in a workplace.
- Approved Document K covers stair geometry — going, rise and nosing projection.
- Approved Document M covers access, and is the source of the 55mm × 55mm contrasting band across tread and riser. It applies to buildings other than dwellings.
- BS 8300-2:2018 is a British Standard referenced by Part M, not law in itself. It defines adequate visual contrast as a difference of at least 30 points of Light Reflectance Value between the nosing and the surrounding tread.
- The Equality Act 2010 creates a duty to make reasonable adjustments. It does not itself specify stair nosings.
- BS 7976 / BS EN 16165 is the pendulum test method behind PTV, and DIN 51130 is the R9–R13 ramp scale.
Put together, a defensible specification on a non-domestic stair looks like this: a 55mm × 55mm profile, in a colour that clears 30 LRV points against the tread, achieving at least 36 PTV wet. Ask the supplier for the LRV figure and the pendulum data rather than accepting "compliant" as an answer — and note that what applies to your project depends on whether it is new build, a material alteration or an existing stair.
Cost over the life of the installation
GRP costs more up front than rubber and slightly more than aluminium. The case for it is not the purchase price, it is that the replacement cycle largely disappears.
Rubber nosings in an exposed position degrade under UV and need replacing several times over the life of a building. Aluminium in a coastal or chemical environment corrodes and gets replaced too. Each replacement carries labour, access equipment and disruption that typically dwarf the material cost — and on a public stair, closure time as well. A GRP installation that is still performing at ten years with nothing spent on it has usually overtaken both on total cost long before then.
Where GRP does not pay is the dry internal stair with light traffic. There, the extra spend buys performance the building will never call on.
Frequently asked questions
What PTV should I specify for an external stair?
At least 36 in the wet, which is the HSE benchmark for low slip potential. Quality GRP typically measures 65 or above wet, so it clears the threshold with substantial margin — useful because surfaces lose some performance as they wear and soil.
Is an R11 rating good enough on its own?
Not really. R ratings come from an oil-wet ramp test in safety boots, which does not describe a rainy stair in ordinary shoes. A single R rating can correspond to a wide span of pendulum results, so ask for the PTV as well — that is the figure the HSE recognises.
How long do GRP nosings last?
Ours are guaranteed for ten years, and installations in sheltered or internal locations commonly run beyond that. Coastal, chemical and heavy industrial environments sit at the shorter end. Because the anti-slip aggregate runs through the surface rather than sitting on it, grip is retained as the material wears.
Can GRP nosings be used on metal stairs?
Yes, and it is a common pairing on outdoor and industrial steel stairs where the metal is already corroding. Use stainless self-tapping screws. The non-conductive surface is an added benefit near electrical plant.
Which grit should I specify?
Medium, around 1mm aggregate, for most stairs. Fine, around 0.5mm, where people are barefoot. Coarse only for heavy industrial or oil-contaminated steps — it is uncomfortable underfoot and abrasive in a fall.
Can GRP nosings be painted?
They can be, with a two-part epoxy system, but it is a poor idea — paint fills the grit texture and reduces slip resistance unless aggregate is added to the paint. The colour runs through the material, so order the colour you want instead.
Will fitting GRP damage the existing stairs?
Properly installed, no. Adhesive fixing avoids drilling entirely. If you are removing old nosings first, take them off with heat and a scraper rather than levering, which limits damage to the substrate underneath.
Can it be installed in freezing conditions?
Mechanical fixing, yes, at any temperature. Adhesive needs the substrate above 5°C to cure properly, so in winter either fix mechanically or warm the substrate first.
Specifying for a project
For most jobs the decision runs: what is the environment, what PTV does the stair need to hold in the wet, does Part M apply, and is this an edge problem or a whole-tread problem. Those four settle profile, grit and product type between them.
Browse the full GRP range for nosings, tread covers, landing covers and strips, or send us the step dimensions and the environment and we will specify against them. Volume pricing, custom lengths and RAL colour matching are available on project quantities, along with material data sheets and test certificates for tender submissions.